1. Field of the Invention
This invention relates to a process for desulfurization of gas streams, such as fuel gas streams, containing H.sub.2 S. The process is particularly suited to high temperature gas streams containing reduced sulfur, such as hydrogen sulfide, wherein the amount of sulfur oxides produced in its removal is reduced, providing an environmentally acceptable off-gas without the consumption of large amounts of energy. The process of this invention utilizes specific solid sulfur removal metal oxide compounds which become sulfided upon removal of hydrogen sulfide from the gas stream and may be regenerated by high temperature oxygen containing gas to result in a substantial portion of the sulfur removed being in the form of elemental sulfur.
2. Description of the Prior Art
Various prior art methods have used oxides of iron, magnesium, calcium and zinc to remove sulfur containing substances, such as hydrogen sulfide, from gas streams at elevated temperatures by chemical reaction. The sulfided metal oxides have then been regenerated by reaction with an oxygen containing gas stream at elevated temperature. However, the regeneration process has generally resulted in off-gases in which the sulfur is primarily in the form of sulfur dioxide, which is environmentally unacceptable. Gas treatment techniques available for removal of sulfur dioxide from such off-gases are available, but substantially increase the cost of the sulfur removal process and consume large amounts of energy.
The desirability of higher elemental sulfur yield from the regeneration of sulfided materials with oxygen containing gases has previously been recognized and attempts have been made to increase the elemental sulfur yield by addition of a reducing agent such as coke, subsequent treatment of the SO.sub.2 containing gas stream with fuel gases over suitable catalyst, and controlling the amount of oxygen admitted during regeneration so that incomplete oxidation of the sulfided material occurs and secondary reactions between the SO.sub.2 and the remaining sulfided masses were encouraged to proceed forming elemental sulfur.
Controlled oxidation of sulfide ores is taught by Australian Pat. No. 157,940 wherein the formation of elemental sulfur is taught to be enhanced by incomplete oxidation of the sulfided material, pyrite containing ores and zinc sulfide containing ores forming about 1 percent elemental sulfur based upon the amount of sulfur in the product gas.